Fish man

If all is going to plan, Martin Strel and his 45-person support team have begun his swim down (up?) the Amazon. He plans to have the 5,400km swim completed by 11 April - as long as he survives the piranha fish, crocodiles, cannibals, and Pororoca (4m tidal wave). Hopefully his support team, traveling in three boats, will be able to distract potentially lethal predators by pouring buckets of fresh animal blood into the water. I'm not sure if that would attract or distract interest in him but it may depend on whether they're with, behind or ahead of him. When it comes to the toothpick fish, though, he's on his own.

The candiru or canero (Vandellia cirrhosa) or toothpick fish is ... found in the Amazon River and has a reputation among the natives as the most feared fish in its waters, even over the piranha. The species has been known to grow to a size of 6 inches in length and is eel shaped and translucent, making it almost impossible to see in the water. The candiru is a parasite. It swims into the gill cavities of other fish, erects a spine to hold itself in place, and feeds on the blood in the gills, earning it a nickname as the "vampire fish of Brazil". (Wikipedia)

If it restricted its activities to fish that might be okay, but it is attracted to urine or blood and swimmers have found themselves the target of the toothpick fish. Once in (through whichever orifice or opening) it's almost impossible to remove the fish except through surgery - by which time the swimmer has usually succumbed to infection, shock and death. But Mr Strel should be okay, as he is quoted by the BBC: "I never urinate straight into the water, I always urinate straight into my wetsuit" - which must be a great relief to those near the Danube, Mississippi and Yangtze Rivers - all of which Mr Strel, a Slovenian, has already swum.
This is probably his most hazardous swim to date - as well as everything else - there's also the possibility of running into poisonous fresh-water stingrays and aggressive bull sharks, which travel far up the river from the Atlantic and frequently attack swimmers, not to mention tarantulas, malaria, dengue fever and rabies spread by bites from vampire bats. Let's hope that 45-person support crew includes a few medics because it seems they might need a little help too!